Insulating blanket and method of forming the same



Ot. 24, 1950 D. JELINEK ET AL INSULATING BLANKET AND METHOD OF FORMING THE SAME Filed Nov. 24, 1947 FIG. 2

FIG. 3

INVENTORS. DONALD JELl/VEK GEO/1 6E G. FEE) ATTORNEY Patented Oct. 24, 1950 INSULATING BLANKET AND METHOD OF FORMING THE SAME Donald Jelinek, Los Angeles, and George C. Frey, Manhattan, Beach, Calif., assignors to North American Aviation, Inc.

Application November 24, 1947, Serial No. 787,656

13 Claims.

This invention pertains to an insulating blanket formed of glass fiber or the like and a method of producing the same.

In the past, considerable difiiculty has been experienced in obtaining insulating blankets having suitable properties for use with exhaust pipes of airplanes and particularly of jet airplanes.

In that connection, it has been found desirable to use leached glass fibers-that is, glass fibers in which the impurities or additiveshave been removed by leaching with acids or the like, leaving glass fibers of almost pure silica. The resulting glass fibers, when formed into mats or batts for the intended purpose, are relatively fiufi'y and hard to handle. Further, it has been found that such flufiy material, when subjected to the temperature of exhaust stacks of jet airplanes, has often shrunk to the point of separation of the fibers, resulting in rupture of the blanket, thereby impairing its insulating functions. It has also been found that the leaching operation in the removal of impurities from the fibers leaves certain of the fibers in a weakened condition. Accordingly, it is desirable to remove the fiufiiness from the insulating blanket without impairing its insulating properties while at the same time obtaining a blanket that is relatively easy to handle and which retains suflicient flexibility so that it can be used for the intended purpose. Further, it is intended to correct for any tendency of the material to break when handled because of having been subjected to the leaching operation.

It is therefore an object of this invention to produce a compact, relatively flexible blanket having high insulating values.

It is a further object of this invention to compact the glass fibers forming the insulating blanket without destroying their flexible properties.

It is yet another object of this invention to provide increased durability of a glass fiber batt While substantially retaining its original flexibility.

Other objects of invention will become apparent from the following description taken in connection with the attached drawings, in which Fig. 1 is a perspective View of an arrangement pertaining to the invention;

Fig. 2 is a perspective view of a glass fiber material which is used in connection with the invention; and

Fig. 3 is a perspective view of a finished blanket made in accordance with invention.

Referring to the drawings, loose fluffy material I, which may be leached to remove impurities or additives therefrom, is placed on a sheet 2 of material which is preferably combustible, such as heavy paper, although it is to be under stood that other materials than paper may be used, such as fabric, fibrous boards, or the like. The sheet material 2 may be smooth but ispreferably irregular in contour by being made crinkled, wrinkled, rippled, or the like. It is preferable to use a paper material which is Only sufi'iciently heavy to obtain the desired indentations in the glass fiber when pressed thereagainst, and one which will leave an unobjectionable residue that will permit separation of the successive layers of the blanket after treatment.

The fiuffy glass fiber material, placed on the sheet material, is subjected to a light pressure sufiicient only to cause the fibrous material to be impressed into the configurations in the sheet material. This may be obtained, as shown in the preferred embodiment of the invention in Fig. 1, by rolling the combined layers of fibrous and sheet material together upon a roll 3, which may be of combustible or non-combustible material, with sufficient compactness to effect the desired result. The roll is then placed in an oven maintained at a temperature sufficiently below the softening temperature of the glass fibers and for a sufficient length of time to cause the material in the glass fiber strands to smooth out and thereby substantially remove any irregularities in the fibers which may have resulted from the leaching operation. This also results in a shrinkage of the glass fiber material with-' out substantial elimination of the number of spaces therein. Accordingly, the insulating properties of the blanket remain substantially the same in the compacted state as in the fiufiy state. Since the heating operation is carried on at a temperature considerably below the softening temperature of the glass fiber, the flexibility characteristics of the glass fiber are not substantially impaired. The crinkled sheet material tends to eliminate any surface tension which may have been imparted to the resulting blanket if a sheet of smooth material had been used, as Well as to obtain a somewhat uniform application of heat throughout the glass fibers. At those points where the crinkled material results in a lessening of the thickness of the blanket, the material adjacent thereto may be heated to somewhat a higher temperature than adjacent areas, thus to provide what may be termed a quilting operation. The sheet material-which serves as a separator and also permits shrinkage of the blanket without ruptureis consumed in the heating operation, leaving only a fine ash. The material has been found to shrink in area as much as 20% during the process.

The oven temperature is maintained at approximately 1600 F. for leached glass fiber material having a softening temperature of approximately 2500 F. the process being continued for l618 hours for an insulating blanket having a resulting thickness of approximately A;-inch. It is to be understood of course that, with glass fiber material having a different softening temperature, the treatment temperature would have to be adjusted accordingly. Also, time-tempera-v ture relations must necessarily be maintained so as to obtain the desired result, it being understood that for lower temperatures the process would have to be continued for a greater period of time than for relatively high temperatures below the softening temperature.

Th soft fiuffy leached glass fiber material which is to be treated according to this invention is in vitreous form as described in the 1928 edition of International Critical Tables, published by McGraw Hill. Heating it to a temperature of approximately 1660 F. for about sixteen hours changes the material to a quartz form according to mentioned tables but not to a tridymite or cristobolite form. The quartz form is referred to herein as partial crystallization. Glass fiber material, as referred to herein, comprises glass fibers from which substantially all the additives which are ordinarily combined with silica to form glass have been removed. In other words, for the purposes of this invention, glass fiber material means substantially purevitreous silica in fiber form.

As a result of this invention there is obtained a compact insulating blanket 4 having substantially the same insulating value as a fluffy blanket with the same amount of material and yet a blanket which occupies considerably less space than a fluffy blanket, one that is easy to handle, and one that will not shrink when subjected to temperatures that may be experienced in con nection with stacks of jet airplanes.

Although the invention has been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example only, and is not to be takenby way of limitation, the spirit and scope of this invention being limited only by the terms of the appended claims.

We claim:

1. The method of producing a compact relatively flexible blanket comprising placing fluffy material of substantially pure vitreous silica in fiber form upon a layer of flexible crinkled sheet material, forming such layers into a roll with only sufficient compactness to cause the fibers in contact with the sheet material to conform to the configurations thereof, and subjecting the resulting arrangement to a temperature below the softening temperature of the fibers and for a sufiicient time only to obtain cohesion of the fibers by partial tively flexible blanket comprising placing fluffy material of substantially pure vitreous silica in flber form between layers of crinkled sheet material, pressing such material until the fibers in contact therewith conform to the configurations thereof, and subjecting the resulting arrangement to a temperature below the softening temperature of the fibers and for a sufficient time only to obtain cohesion of the fibers by a partial crystallization thereof.

6. The method of producing a compact relatively flexible blanket comprising placing fiulfy material of substantially pure vitreous silica in fiber form between layers of crinkled combustible sheet material, pressing the sheet material until the fibers in contact therewith conform to the configurations thereof, and subjecting the resulting arrangement to a temperature below the softening temperature of the fibers and for a sufiicient time only to obtain cohesion of the fibers by partial crystallization thereof.

7. The method of producing a compact relatively flexible blanket comprising placing flufiy material of substantially pure vitreous silica in fiber form between layers of crinkled paper, pressing the paper until the fibers in contact therewith conform to the configurations thereof, and subjecting the resulting arrangement to a tempera ture below the softening temperature of the fibers and for a sufficient time only to obtain cohesion of the fibers by partial crystallization thereof.

8. The method of producing a compact relatively flexible blanket comprising placing fluffy material of substantially pure vitreous silica in fiber form having a softening temperature of approximately 2500 F. between layers of crinkled combustible sheet material, pressing the sheet material until the fibers in contact with the sheet 7 material conform to the configurations thereof,

'and subjecting the resulting arrangement to a temperature of approximately 1600 F. for a suificient time only to obtain cohesion of the fibers by partial crystallization thereof.

9. The method as recited in claim 8' in which the time is approximately 15 hours.

10. An insulating blanket characterized by being composed of cohering material of substantially pure vitreous silica in fiber form which has been shrunk and compacted by heat'treatment below the softening or slumping temperature thereof by subjecting the material to a temperature of about 1600" F. for about sixteen hours-to facilitate handling of the blanket without substantial impairment of its insulating properties-and in which the surface 'of'the blanket is provided with crinkled configurations retained in the crinkled shape by the partial crystallization of the fibers as a result of the heat'tre'atment.

11. An insulating blanket as'provided in claim' 10 in which the fibers in'srnall scattered areas thereof are crystallized to a greater extent than those in the remaining interconnecting areas to provide a quilting effect.

12. The method of producing a compact, relatively flexible blanket comprising placing fluffy material of'substantially' pure vitreous silica in fiber form between layers of sheet material; lightly pressing the sheet material into contact with the fiber material, and subjecting the resulting arrangement to a temperature below the softening temperature of the fibers for 'a sufficient time only to obtain cohesion of the fibers'by partial crystallization thereof.

13. The method of producing a compact, relatively flexible blanket comprising 'subjecting'a batt of fluffy material of substantially pure vitreous silica in fiber form having a softening temperature of approximately 2500 F. to a temperature of approximately 1600 F. for approximately 16 hours.

DONALD JELINEK. 5

GEORGE C. FREY.

REFERENCES CITED The following references are of record in the m file of this patent:

UNITED STATES PATENTS Number Name Date Thomas Oct. 8, 1935 McClure Sept. 5, 1939 Collins Oct. '7, 1947 No-rdberg Feb. 15, 1949 

